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  • 1
    ISSN: 0947-3440
    Keywords: Conjugation ; X-ray diffraction ; Molecular structures ; Ab initio calculations ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Low temperature crystal structural studies of small cyclopropyl-conjugated unsaturated hydrocarbons reveal significant differences in bond lengths between carbon atoms mainly within the three-membered rings but also for adjacent C—C single bonds. The strongest influence of conjugation was observed for spiro[2.4]hepta-4,6-diene (1), where the difference in the lengths of three-membered ring bonds is 0.050 Å (X-ray). The same effect is also obvious from ab initio calculations at HF/6-31G(d) (to a minor extent) and MP2/6-31G(d) levels, as shown by a difference analysis of bond lengths which was performed in order to cancel out systematic errors and differences for both methods. Static difference electron density maps were derived from the experimental data by multipole refinements. These maps showed shifts of electron density to exocyclic locations within the planes of the three-membered rings and significant bond ellipticities for the adjacent single bonds. For 1,1-diethenylcyclopropane (4) a nonsymmetric conformation was found in the crystal lattice, very close to the global minimum structure calculated by ab initio methods.
    Additional Material: 7 Ill.
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  • 2
    ISSN: 0947-3440
    Keywords: Bicyclopropylidene ; Spiro compounds ; Cycloadditions ; Amino acids ; Cuprates ; Tetrahydropyridines ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reactions of ethyl 2-acetoxy-2-diphenylmethyleneaminoacetate (1) with organocopper reagents derived from bicyclopropylidene (2) and methylenecyclopropane (3) are accompanied by an unusual mode of opening of one three-membered ring to give 4-methylene-1,2,3,4-tetrahydropyridine derivatives 8a, 9 in good yields. The cuprate derived from methylenespiropentane (4) reacts with 1 to yield both the normal substitution product 14 (37%) as well as the rearrangement product 15 (34%), while the simple cyclopropylcuprate undergoes substitution to give the protected cyclopropylglycine 16 (75%) without rearrangement. The tetrahydropyridine 8a shows an interesting tautomerism in solution. The 4-cyclopropylidenetetrahydropyridine 15 undergoes an unusual dehydrodimerization to produce two separable rotamers, C2-19 and C1-19, via 18.
    Additional Material: 3 Ill.
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford [u.a.] : International Union of Crystallography (IUCr)
    Acta crystallographica 57 (2001), S. 968-969 
    ISSN: 1600-5759
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: The central three-membered ring in the title compound, trans-1,1′,1′′-cyclopropane-1,2,3-triyltris(cyclopropanol), C12H18O3, shows pronounced asymmetry of the bond lengths, which is induced by the different orientations of the substituents. A network of hydrogen bonds links the molecules into sheets.
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  • 4
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 29 (1991), S. 774-776 
    ISSN: 0749-1581
    Keywords: 13C NMR ; Polyspirocyclopropanes ; Triangulanes ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The 13C NMR spectra of triangulanes, the unique class of hydrocarbons constructed from spiroannulated cyclopropanes, were analysed, and correlations were revealed between their structures and 13C chemical shifts. The procedure for the configurational assignment in triangulanes based on the 13C NMR spectral data is described.
    Additional Material: 1 Ill.
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  • 5
    ISSN: 1434-193X
    Keywords: Amino acids ; Bicyclopropylidene ; Methylenecyclopropane ; Palladium catalysis ; Zinc reagents ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Palladium-catalyzed cross-coupling reactions of bromo(methylenecyclopropanes) 1c, 2c with the sodium enolate of dimethyl malonate 4a and the chlorozinc enolates of the glycine equivalent (diphenylmethyleneamino)acetate 4c and diethyl malonate 4d, respectively, have been found to proceed with opening of the three-membered ring in each case, to give the corresponding dienyl-substituted CH-acidic compounds 5-7 in moderate to good yields. On the other hand, coupling of bicyclopropylidenylzinc chloride (2d) with diethyl bromomalonate (4e) and the electrophilic glycine equivalent ethyl 2-acetoxy-2-(diphenylmethyleneamino)acetate (4f) gave 7 and 6 in 27 and 29% yield, respectively.
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  • 6
    ISSN: 1434-193X
    Keywords: Antibiotics ; Dipeptides ; Heterocycles ; β-Amino acid ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: TAN-1057 (1a, b) - a new natural dipeptide antibiotic active against methicillin resistant strains of Staphylococcus aureus - was synthesized starting from Nα, Nδ, Nω-tri-Z-L-arginine 20b via the corresponding diazoketone 21b. This upon photolysis rearranged to the ketene which was trapped by (±)-2,4,5,6-tetrahydro-5-methylamino-2-ureidopyrimidin-4-one (3) to yield the fully protected dipeptide 23 (30%). The latter was deprotected by hydrogenolysis to give the final compound as a mixture of two epimers - TAN-1057A, B - isolated previously from a strain of Flexibacter sp. PK-74. The intermediate 3 was prepared from 3-amino-2-(N-Z-N-methylamino)propionic acid methyl ester hydrochloride (16) and 2-methyl-2-thiopseudobiuret hydroiodide (18) in one step in 35% yield.
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  • 7
    ISSN: 1434-193X
    Keywords: Bicyclo[1.1.1]pentane ; Haloarenes, cross-coupling of ; Propellanes ; Palladium ; Catalysis ; Small-ring systems ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -Radical addition reactions of organyl iodides 7a-s onto [1.1.1]propellane (2) followed by halogen-lithium exchange and transmetallation with zinc chloride, as well as additions of Grignard reagents to 2, have furnished a variety of 3-substituted bicyclo[1.1.1]pentyl-1-magnesium (14) and -zinc (19) derivatives. The latter have been coupled with various alkenyl, aryl, and biaryl halides and triflates under NiCl2dppe, Pd(PPh3)4, or PdCl2(dppf) catalysis to give a number of 1,3-disubstituted bicyclo[1.1.1]pentyl derivatives 17, 20, and 23, several of which exhibit liquid crystalline properties, in moderate to very good yields. The coupling products 20ca, 23ab, 23ae, 23ff, and 23fg have been further transformed to yield bicyclo[1.1.1]pentyl derivatives 32, 24ab, 24ae, 27ff, and 27fg, respectively, bearing alkynyl, cyano, and/or alkenyl groups.
    Additional Material: 7 Tab.
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  • 8
    ISSN: 1434-193X
    Keywords: Bicyclopropylidene ; [3 + 2] Co-cyclization ; Nickel(0) catalysis ; Palladium(0) catalysis ; 4-Methylenespiro[2.4]heptane derivatives ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Bicyclopropylidene (1) readily undergoes a palladium(0)-catalyzed [3 + 2] co-cyclization with electron deficient alkenes (methyl acrylate, methyl trans-crotonate, methyl cinnamate and diethyl fumarate) as well as with some strained alkenes (norbornene, norbornadiene) by distal ring cleavage of one of the three-membered rings of 1. All these co-cyclizations are regioselective with respect to 1 as well as regio- and stereoselective with respect to the alkenes to give the corresponding 4-methylenespiro[2.4]heptane-trans-6-carboxylates 2a-5 with the electron deficient alkenes and the cycloadducts 6 and 7 with the strained alkenes in acceptable to good yields (56 to 83%). In contrast to palladium(0) catalysts nickel(0) complexes catalyze both distal ring opening of 1 and oxidative coupling of the two double bonds when 1 is reacted with e.g. diethyl fumarate. The result is a mixture of the methylenecyclopentane derivative 5 with the [2 + 2] cycloadduct 8 and the cotrimer 9.
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  • 9
    ISSN: 1434-193X
    Keywords: Radical reactions ; Spiro compounds ; Additions ; Sulfides ; Amino acids ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The addition of thiols 8a-h onto the double bonds of bicyclopropylidene (1) and methylenespiropentane (2) proceeds quantitatively in benzene at 20 to 75 °C in the absence of catalysts or radical initiators to give products 9, 10 with complete retention of both three-membered rings. Methylenespiropentane (2) yields exclusively the anti-Markovnikov adduct 10. The unsubstituted methylene-cyclopropane (3) gives 9% of the ring-opened compound 12 in addition to the anti-Markovnikov adduct 11. The addition of thiols to n-heptylbicyclopropylidene (13), methylenecyclopropylacetic acid (15), and the amino acids 17, 19 containing bicyclopropylidene or methylenespiropentane fragments, does not proceed stereoselectively, though in all cases the mercapto function adds to the double bond with retention of the cyclopropane ring to give interesting new amino acids containing bicyclopropyl and spiropentyl fragments, respectively. The probable mechanism of this thiol addition is discussed in the light of a test with the cyclizing intramolecular addition of 2-(2-methylenecyclopropyl)ethanethiol 27.
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  • 10
    ISSN: 1434-193X
    Keywords: Amino acids ; Spiro compounds ; Michael addition ; Copper reagents ; Curtius degradation ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Racemic spiropentylglycine (8) has been synthesized by sodium borohydride reduction of benzyl (E/Z)-2-chloro-2-spiropentylideneacetate (5-Bn), nucleophilic substitution of the chlorine in the product 6 with azide and hydrogenolytic deprotection of the resulting 7 (overall yield 15%). An alternative approach to 8 consisted of the coupling of the higher-order cuprate 10, generated by halogen-metal exchange from bromospiropentane (9), with the electrophilic glycine equivalent 11 followed by deprotection (overall yield 47%). Enantiomerically pure (1′-aminospiropentyl)acetic acid [(R)-16] (overall yield 16% from 5-Me) and 1-aminospiropentanecarboxylic acid [(R)-23] (29% from 5-Me) were obtained from the Michael adduct 14-Me of (4R,5S)-4,5-diphenyloxazolidin-2-one (13) and methyl (E/Z)-2-chloro-2-spiropentylideneacetate (5-Me). Racemic 1-aminospiropentanecarboxylic acid (R/S-23) was prepared by rhodium-catalyzed addition of dimethyl diazomalonate to methylenecyclopropane and subsequent Curtius degradation of the halfester 28 via the azide 29 (overall yield 14%). Upon standing in aqueous solution, 23 underwent complete rearrangement to the new 1-amino-2-methylenecyclobutanecarboxylic acid (24). The interesting derivative of azabicyclo[3.1.0]hexane-1-carboxylate 34 with an annelated spiropentane moiety and a β-amino acid fragment was incidentally obtained in a one-step intermolecular domino reaction starting with the addition of lithium benzylamide to methyl 2-chloro-2-cyclopropylideneacetate (32, 41% yield).
    Additional Material: 2 Ill.
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